Indoor water heaters of the domestic type usually comprises an upright generally cylindrical body including a tank for holding a quantity of water to be heated. A burner for natural gas, propane or other fuel is disposed within a combustion chamber which is associated with the lower region of the water heater tank to conduct the heat of combustion to the water contained in the tank. The combustion chamber includes a combustion air inlet opening and a flue gas outlet opening. A flue pipe extends from the flue gas outlet opening to a position at the exterior of the water heater body where a connection is made between the flue pipe and a chimney or other passageway leading to the outdoor atmosphere. The flue pipe usually extends through the tank of water in order to conduct additional heat into the water from the flue gases.
A particular type of conventional water heater employs an atmospheric burner to provide the heat of combustion at the combustion chamber. Combustion of fuel in the atmospheric burner normally derives necessary oxygen from the air surrounding the burner and the water heater. The products of combustion are vented by means of a natural draft developed by the heat of combustion at the burner as opposed to a draft driven by a fan or blower. Room air is drawn into the combustion air inlet opening as the heat of combustion causes flue gases and heated combustion air to flow through the flue gas outlet opening and upwardly through the flue pipe to the chimney connection.
Atmospheric burner water heaters of this type suffer from several disadvantages. The greatest disadvantage arises in the use of room air for combustion air at the burner. Use of room air inefficiently wastes the energy expended to heat, cool, or humidify that air since it is wastefully driven out of the building with the exhaust of flue gases. A further loss of room air occurs through the open arrangement of the vent hood over the flue pipe which permits room air to pass through the annular space therebetween and upwardly to the chimney with the rising flue gases. Another disadvantage is that the heated interior components of the water heater cause a residual convective flow to proceed through the water heater between intermittent operations of the burner. This not only wastes room air being drawn in through the combustion chamber inlet opening, but also wastes heat which is consequently drawn out of the heated components and the stored quantity of water by the residual convective flow. Furthermore, a draft of room air out of the building through the water heater tends to cause a corresponding draft of outdoor air into the building through cracks or other spaces in door and window frames to further disrupt heating or air conditioning systems.
Another type of domestic indoor water heater employs a power burner to provide the heat of combustion. A power burner is a device for providing a mixture of gaseous fuel and combustion air which is calculated to increase the efficiency of fuel consumption. A water heater system employing a power burner generally uses a centrifugal blower in a housing adapted to cause a pressurized flow of combustion air which is mixed with fuel and directed to the combustion chamber of the water heater. The flue pipe in such heaters may extend from the combustion chamber outlet opening through the tank of water in either a straight or an non-linear configuration to a position at the exterior of the water heater where a connection is made to a chimney or conduit extending to the outdoor atmosphere. A combustion air inlet conduit may be provided to extend from the outdoor atmosphere to the combustion chamber inlet opening to complete a driven draft direct vent system which vents the combustion chamber to the outdoor atmosphere in isolation from indoor room air. One such water heater is described in U.S. Pat. No. 4,766,883 assigned to the assignee of this application.
Water heaters having power burners also suffer from several disadvantages. A complex control system is required to operate the gas valve and to operate the blower. A complex fuel pressure regulating device requiring precise adjustment upon installation is often used. Power burner systems also disadvantageously consume electricity to drive the centrifugal blower and to operate the control system in addition to the consumption of gaseous fuel. Centrifugal blowers consume greater amounts of electrical energy than do simple propeller fans, but are used in order to meet the pressure requirements of the power burner as well as to drive the venting flow. Furthermore, if a direct vent system is not provided and combustion air is drawn from the surrounding room instead of from the outdoor atmosphere, the higher pressure requirements of the power burner system will cause an even greater loss of conditioned room air than is experienced in the natural draft atmospheric burner systems described above.
It is sometimes desirable to employ the heated water from the water heater to heat room air in the building in which the water heater is installed. Water heaters having power burner systems are known to have been adapted for this purpose. Heated water is pumped from the tank in the water heater to a coil exposed to the room air, and is returned to the tank in a cycle separate from the ordinary flow of hot and cold potable water through the water heater and associated plumbing. The coil is associated with an existing space heating system at an air duct or plenum. Such attempts to provide a combination water heater-space heater thus require plumbing connections to be made through the room space between the water heater and the existing space heating system, and disadvantageously occupy and limit available room space in utility rooms or other similarly cramped indoor locations where these appliances must be installed. Such systems also require an "engineered" approach in that matching of the water heater to existing or available space heating components can be complex.
Disadvantages common to both atmospheric burner and power burner systems include the location of the gas valve and associated components at the exterior of the water heater body. Exposure of these components could subject them to damage upon shipment or installation, or to improper adjustment by untrained personnel after installation. These components also present a somewhat inappropriate appearance for a finished basement utility room, laundry room or other common household location of a water heater.
Known water heaters are thus seen to fail to provide a venting system which efficiently operates in isolation from indoor room air without requiring the use of complex electrical components such as fluid pressure regulators and energy consuming centrifugal blowers, or to provide an unobtrusive and compact arrangement of components to serve as a combination water heater and space heater.
In the co-pending application Ser. No. 268,716 of which this application is a continuation-in-part, an invention overcoming many of the above-referred to disadvantages is disclosed. The invention provides for an indoor domestic type gas heater having a driven draft direct vent system for an atmospheric burner. The invention is also adaptable for use as a combination water heater and space heater. This system provides not only for the heating of water for human consumption and use, but also for the heating of indoor room air.
The space heater is located atop of the water heater and includes a coil in a closed cycle water loop extending between the water heater tank and the space heater. The space heater is adapted to heat room air by flow across the coil heated by hot water from the water tank.
Although the vertical alignment of the water heater and space heater is a compact and space saving arrangement, elements such as the pipe linkage and an associated pump for communicating water between the two components is exposed. Moreover, the linkage prevents easy attachment and separation of the two components. Consequently, skill and knowledge of the structure is necessary to replace and/or separate the water heater from the space heater should either need replacement or repair.